Process of making pistons



F. A. PARKHURST.

PROCESS OF MAKING PISTONS.

APPLICATION FILED DEC. 19, 1917- 1,3'70,553, Patented Mar. 8, 1921;

3 SHEETS-SHEET I 5 H J fif 1 4 ff I I d z K I I F. A. PARKHURST.

PROCESS OF MAKING PISTONS.

APPLICATION FILED DEC. 19, I917. 1,370,553, Patented Mar. 8, 1921.

3 SHEEISSHEET 2.

fnyezzfof F. A. PARKHURST.

PROCESS OF MAKING PISTONS.

APPLICATION FILED 050.19.1912.

Patented Mar. 8, 1921.

3 SHEETS-SHEET 3- by WV conformation. By such a method, the origireferred to of suc UNITED STATES PATENT II-OFFICE.

FBEDEBIC A. 19533311381, 01 CLEVELAND, OHIO, ASSIGNOR TO THE ALUMINUM GASTINGB COMPANY, 01 CLEVELAND,'OHIO, A CORPORATION OF OHIO.

PROCESS OF MAKING- PISTONS.

Specification of Letters Patent.

Patented Mar. 8, 1921.

. Application filed December 19, 1917. Serial No. 207,836.

To all whom it may concern:

Be it known that I, FREDERIC A. PARK- HURST, a citizen of the United States, resid- This invention relates to pistons for internal combustion engines and to. an improved process of making them, the invention having to do more especially with pistons of the t shown in the patent to Spillman and 00ers, No. 1,092,870.

One object of the invention is the production of a piston of the type last referred to formed of metal of low specific gravity, such as a suitable aluminum alloy, and having an internal structure and other physical characteristics which mark such alloys when cast in permanent molds.

Another object of the invention is the production of an im roved piston of the type K a character that compli cated core work is obviated.

A further object of the invention is the production of an improved piston of the type in question having a form and constituent material such that it can be formed either in whole or in part by (1) casting and (2) further shaping the cast structure by drawing, spinning, rolling or other form of swa g operation.

Anot er object of the invention is the provision of an improved process of making pistons of the type above mentioned. istons of the type in question comprise a head part with an end wall and a cylindrical side wall and a guide part or trunk having an inner wall, wluch is preferably formed with wrist pin bosses, and an outer cylindrical, cylinder-engaging wall. Briefly stated, my improved process consists in making a piston casting of metal capable of being swaged, with the metal of either or both the side wall. of the head and the outer wall of the trunk in the form of an outwardly extending flange and thereafter by spiunin or other swaging operation, turning suc flange or flanges to cylindrical nal casting is simplified to such an extent that it is possible to produce it in a permanent mold and thus give the metal of the finished piston physical characteristics which are peculiar to the rapid chilling action of the permanent mold.

For the purpose of explaining the character of my improved piston and the process of produclng it, I have illustrated in the accompanymg drawings several forms of construct on and have indicated the successive steps in carrying out the process.

In the drawings, Figure 1 is a side elevation, partly in section, of a piston casting whlch represents the first step of my improved process.

Fig. 2 is a central vertical section of the .same piston casting after a portion of the flange which is to form the outer wall of.

the trunk has been machined away preparatoiiy to the next step of the process.

' 1 3 is a view similar to that ofFig. 2 but s owing the outwardly extending flange spun u ward to form the cylindrical outer wall 0 the trunk.

Fi 4 is a view similar to that of Fi but s owing the piston after the removal machining of. superfluous metal.

F1 5 1s a view similar to the last, showmg e piston completed by machining operatlons.

Figs. 6 and 7 are side elevation and bot- :om plan, respectively, of the finished pis- Fig. 8 is a side elevation, partly in section, of a piston illustrating a modified form of construction.

Fig. 9 1s a fra enta side elevation, partly in section, 1 lustrating the first step in the process of making the piston shown a in Fig. 8.

Fig. 10 is a central vertical section of a designates the head part of the piston in its entirety and 2 designates the trunk part of the piston in its entirety. The head 1 comprises an end wall 1 and a side wall 1", while the trunk or guide part of the piston has an inner wall or section 2 and an outer cylinder-engaging wall 2". The trunk or guide part of the piston preferably also perorms the function of connecting the piston to the connecting rod and to that end is formed with wrist pin bosses 2, 2 the latter boss being formed with an enlargement 2* to receive the usualset screw. The head and trunk are also preferably formed with strengthening and heat dissipating ribs 2, 2

In its finished form, the lateral wall of the piston head is provided with grooves 3 to receive the usual packing rings (not shown), and said lateral wall has a diameter such that it never closely fits the engine cylinder. e

The outer wall 2 of the trunk is connected with the inner wall thereof only at its lower end, so that heat conducted from the end wall of the piston head must traverse the entire length of the piston before reaching the outer guide wall 2 and therefore much of this heat is dissipated by radiation and contact with the air and vapors of the crankcase before it reaches said outer wall 2, so that said outer wall is maintained at a relatively low temperature and can, therefore, fit relatively closely in the en ine cylinder.

1 Pre erably, a series of holes 1, 4 are formed at the bottom of the piston between the inner wall 2* and the outer wall 2 to permit lubricant and oil which enters the. space between said walls to drain freely .back to the crank case.

In the production of the iston illustrated in-Figs. 5, 6 and' 7, the cordance with my improved process, is the .making of the casting shown in Fig. 1. This casting is preferably formed of a metal of low specific gravity such as the aluminum alloys now extensively employed in the making of pistons and in a suitable permanent mold. I preferabl employ a mold and process such as is set orth in Letters Patent, No. 1,296,589, granted to Joseph H. Bamber and such as is also illustrated in Letters atent, No. 1,296,596, granted to me, both dated March 4, 1919. When a suitable aluminum alloy is cast in molds'of the character referred to, the metal of the casting as compared with the same metal cast. in

molds of relatively low conductivity is given a hard, fine grained, ductile structure with rst step, in ac-- the spinning operation, the inturned rib or flange 5 serves to greatly stiffen the piston structure sothat the pressure of the spinning tool is adequately resisted. After the spinning operation, the rib 5 is machined away, the lower outer corner of the piston is rounded as at 7 and the upper edge of the trunk wall 2 is trimmed away, with the resulting structure shown in F i 4. a

Finally, the machining of the ring grooves 3, the drilling of the. lubricant holes '4. and the recessing of the wall 2* at 8 to permit the introduction of the wrist pin and the other usual finishing operations, gives the finished piston shown in Figs. 5, 6 and 7 g In machining the outer side walls of the piston, as has been indicated, the outer diameter of the wall 2 is made such that said wall has a relatively close fit in the engine cylinder while the side wall 1" of the head has a loose fit, the wall 2 being relied upon to guide the piston in its movement in the cylinder.

By means of my improved process I not dent to the casting of prior pistons of this type, but also have roduced an integrally cast piston having t e advantages peculiar to pistons of this-type with the added advantages of light weight and the hereinbeonly avoid the complicated core work incifore mentioned physical characteristics peculiar to aluminum alloys cast in permanent molds.

. Turning to the form of construction illustrated in Fig. 8, the finished piston comprises a head part'designated in its entirety by lland a trunk part designated in its entirety by 12. The head comprises an end wall 11 and a cylindrical side wall '11". This latter side wall is formed, in the present case, independently of the trunk of the piston which comprises an inner wall 12 and a cylindrical outer wall 12", the said inner wall joining the end wall of the piston head at points radially inside of said side wall 11 of the head, while the outer wall 12 is connected with the inner wall only at the lower end of the iston. The inner wall of the piston trunk is preferably formed with wrist pin bosses 12, 12*, the last named boss being formed with a set screw enlargement 12. The inner wallof the trunk and the end wall of the head are formed with strengthening and heat dissipating ribs 12, 12 12 The side wall 11 is formed in the usual manner with grooves 13 to receive packing rings and preferably also with lubricant grooves 14 also a suitable number of lubricant apertures 15 are provided at the bottom of the piston and the outer wall 12 of the.

trunk is recessed at 16 to permit the entry of the wrist pins in the-bosses 12, 12.

In the production of the piston shown in Fig. 8, the first step, in accordance with my process is. the formation of the casting shown in Fig. 9, this casting being formed of suitable aluminum alloy or other metal in permanent molds as has been set forth in connection with the first form of construction. In this casting. it will be observed that the metal of the finished side walls 11 and 12 are in-the form of outwardl extending flanges 11 and 12" respectively. After the machining or trimming of flange 11 to the form indicated by the dotted lines, it and the lower flange 12" are spun or otherwise worked downward and upward respectively, to form the cylindrical side walls 11 and 12 and thereafter trimming and machining operations are carried out similar or analogous to those described in connection with Figs. 1 to 7, resulting in the. finished piston shown in Fig. 8.

The construction shown in Fig. 10 is in many respects similar to that shown in Fig. 5 and comprises a head part 21 having an end wall 21 and a cylindrical side wall 21", and a guide or trunk part 22 having an inner wall 22 and a cylindrical outer wall 22 The inner wall of the trunk is formed with wrist pin bosses 22, 22", the boss 22 having 4 a set screw enlargement 22 and internal ribs 22 and 22 are provided as in the first form of construction. The side wall 21 is form'- ed with the usual grooves '23 for packing rings, a series of In ricant apertures 24 are provided at the bottom of the piston and the side wall 22 is recessed at 25 to ermit the introduction of the wrist pin. T' is last form of construction differs from the first form principally in the manner in which the outer wall 22 is. formed.

As shown in Fig. 11, the outwardly extending flange 22 of the original casting is formed, either by casting or machining, with a shoulder 26. In the subsequent spinning operation by which the flange 22 is formed into the cylindrical wall 22, the shoulder 26 affords a firm abutment for the metal of the flange as it is spun inward and upward, as will readily be understood.

The trimming and machining operations subsequent to the spinning operation are similar in this case to those described in connection with Figs. 1 to 7 and need not be further referred to.

.tendin I have herein referred to the use of metals or metallic alloys of low specific gravity and it is to be understood that I mean by these terms metals or alloys whose specific avities are low in comparison with that of iron, the metal of which pistons have commonly been made in the past.

It will be understood that the foregoing description of certain embodiments of my invention is not intended to define or limit the invention but is of explanation and illustration, the scope of the invention being indicated by the following claims. I

What I claim is:

l. The process of making trunk pistons having a head with an end wall and a cylindrical side wall and a trunk with an inner wall and a cylindrical outer wall, which consists in inte ally casting ofmalleable metal the head an trunk parts with an outwardly extending flange on one of said parts, and thereafter swaging the metal of said flange to form one of the said cylindrical walls.

2. The process of making trunk pistons which consists in integrally casting of malleable metal the piston head and trunk with an outwardly extending flan e at the bottom end of the trunk, and thereai ter swaging the metal of said flange upwardly to form a cylinder-engaging guide wall.

3. The process of making trunk pistons having a head with an end wall and a cylindrical wall and a trunk with an inner wall and a cylindrical outer wall, which consists in integrally casting of aluminum alloys in molds of high thermal conductivit the head and trunk parts with an outwar y exflange on one of said parts, and

therea erswaging the metal of said flange 1 to form one of the said cylindrical walls.

4. The process of makin trunk pistons which consists in 'inte a ly casting of aluminumalloys in mol s of high thermal conductivit the piston head and trunk with I an outwar ly extending flange at the bottom end of the trunk and thereafter swaging the metal of said flange upwardly to form a cylinder-engaging guide wall.

5. The "process of ma drical side wall and a trunk with an inner wall and a cylindrical outer wall, which consists in integrally casting of aluminum ing trunk pistons 1 having a head with an end wall and a cylinat the bottom end of the trunk, and thereafter swaging the metal of said flange upwardly to .form a cylinder-engaging guide wall.

der-engaging guide wall and removing the said inwardly extending flange.

8. The process of making trunk pistons which consists in integrally casting of malls"- able metal the piston head and trunk with an outwardly extending flange at the bottom end of the trunk, forming the outwardly turned flange with a. cylindricalshoulder on its upper side, and swaging the said flange upward against the said shoulder to form a cylinderengaging guide wall.

9. The process of making trunk pistons which consists in integrally casting of malleable metal the piston head and trunk with an outwardly extending flange at the bottom end of the trunk, swaging the metal of said vflange v upwardl engaging guide wal and trimming away the up er end of the said guide wall.

10. he process of making trunk pistons which consists in-integrally casting of ma1le-' able metal the piston head, trunk and wrist pin bosses of. said trunk with an outwardly extending flange-at the bottom end of the trunk, swaging the metal of said flange up- -wa'rdly to form a cylinder-engaging" guide wall, and cutting away said guide wall at points adjacent the pin bosses to permit introduction of the pin. I

In testimony whereof Iaflix my signature, in the'presence of a witness. I

' FREDERIC A. PARKH URST. Witness:

THERESA LAVEN.

to form a cylinder- 

